Cisco CUCM NTP Configuration

Properly configuring your CUCM server to get time from a valid time source via NTP is an easily overlooked CUCM configuration step.  You can inherit all kinds of problems down the road if you do not synchronize all of the network and voice devices within your solution.

This post is intended to give you a quick walk-through on how to configure CUCM to use an external NTP server to synchronize it's time.

Note:  Do not confuse this with "Phone NTP References".  You can optionally configure phone Network Time Protocol (NTP) references in Cisco Unified Communications Manager Administration to ensure that a phone that is running SIP gets its date and time from the NTP server.  If you choose not to do so, SIP phones will get time from the 200 OK SIP messages they receive.

Cisco CUCM NTP Configuration Steps
  1. Access the "Cisco Unified OS Administrator" on the CUCM Publisher.
  2. Settings > NTP Servers
  3. NTP Server Settings:  [ enter the IP Address of the NTP server here ]
Select a device running the NTP server that is stable within your network and if possible, has access to a publicly reachable (atomic) NTP source.  After adding the NTP server above, you'll need to restart all the servers in the cluster for the change to take effect.

CUCM NTP Verification

From the CLI, use the utils ntp status command as shown below.  In the example shown, the CUCM server is synchronized to NTP server ( at stratum 3.

admin:utils ntp status
ntpd (pid 30521) is running...

     remote           refid      st t when poll reach   delay   offset  jitter
*    2 u  780 1024  377   49.199   -1.620   0.456
synchronised to NTP server ( at stratum 3
   time correct to within 45 ms
   polling server every 1024 s

Current time in UTC is : Thu May 27 16:59:47 UTC 2010
Current time in America/Chicago is : Thu May 27 11:59:47 CDT 2010

You can run this on each server within the cluster and you should see that the CUCM Publisher is synchronized with the NTP server entered above.

All other servers in the cluster will be synchronized with the CUCM Publisher.

Related Posts:
Cisco IOS NTP Overview
Cisco IOS NTP Configuration

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